1. Field of the Invention
The present invention relates to the cutting and pinning of muntins. More particularly, the present invention pertains to devices for cutting and pinning muntins. Even more particularly, the present invention concerns a system for cutting and pinning muntins.
2. Description of the Prior Art
Traditionally, muntins, or muntin strips, have been used as decorative dividers or spacers between or outside panes of glass used for windows and doors. The muntins render the panes of glass aesthetically appealing. Because the muntins are frequently utilized between glass panes, they must present a flat mating surface to prevent the glass from mis-seating against them. A flat surface is reasonably easy to sustain if the muntins are all aligned in a single direction. However, it becomes more difficult to sustain a flat mating surface at an intersecting joint of two muntins laid out in different directions or in other directional configurations.
Another common problem is separation of the muntins, which may occur at intersecting joints over a period of time. This destroys both the designs created with the muntins and the aesthetic quality provided to the window by the placement of the muntins.
Several methods for assembling muntins to provide flat and strong intersecting surfaces are known. For example, muntin sections have been welded together to create a solid grid-type lattice structure, and then ground at the weld to eliminate rough surfaces created by the weld. However, the welded strips, although structurally solid, create other problems. Glass panes, whether in a window or a door, expand in warm temperatures and contract in cold temperatures. To accommodate for this expansion and contraction, the muntins must be flexible. Welded muntins tend to be inflexible, which causes the glass panes to eventually crack. Also, the grinding of the weld does not produce consistently flat surfaces at the weld. This promotes stress on the glass panes. Further, heat from welding occasionally causes the muntins to warp, which also causes stress on the glass panes.
Thus, other methods and devices have been developed to provide muntin grid assemblies that are reasonably solid and flexible. A typical example of this is the keeper developed by Allmetal, Inc. of Itasca, Ill. The Allmetal keeper is a plastic keeper or connector that is used to join muntin sections, wherein each plastic keeper is installed in a first muntin section. Additional muntin sections are then mounted onto each keeper to form a grid.
An alternate keeper is that developed by Hygrade Metal Moulding Manufacturing Corp. of Farmingdale, N.Y. The keeper sold by Hygrade has a different configuration than that of Allmetal, but is used in a similar fashion to that of Allmetal in that each keeper is installed in a first muntin section and additional muntin sections are then mounted onto each keeper to form a grid.
Although the keeper systems of Allmetal and Hygrade provide structured flexibility, both solidity and flexibility in lattice design are limited because of the shape of the joining ends of the muntin sections in these systems. The ends of muntin sections are commonly square cut, as needed, to mate flush against another muntin. However, problems arise when muntin sections are not shaped to receive a square cut. The square or flush cut has a tendency to rock or separate from a flush fit during assembly and use, even though the muntin section is seated on a plastic keeper. The rocking may cause bent edges which, if not caught during inspection, may contact the panes of glass, thus causing stress points on the panes of glass. Also, the joint may come apart during use, thus destroying the aesthetic appearance of the lattice.
Hygrade Metals, in addition to developing keepers, has attempted to address the above problem by notching muntin sections that are used in crossbar assemblies. The notched muntins are interlaced, one on top of another, with the notches facing each other. In most cases, the notches permit the two muntins to merge to the thickness of one muntin. However, if there is not an exact merger, the intersecting surfaces are not flat. Again, this provides stress on glass panes. Also, upon assembly and use, the expansion and contraction of the glass and metal due to changes in temperature causes the intersecting muntins to separate and the glass to contact the muntin, this creating stress on the glass panes.
It is also noteworthy that the assembly process generally used to assemble the muntins involves cutting the muntin sections either by routing or with a single, stationary blade or cutter that produces a square cut. Routing leaves large burrs that present assembly problems if not removed. To obtain an angle cut, a muntin is positioned at a desired angle and then cut by the single blade. The muntin sections are next either punched with a hole or are notched. The punched and notched muntin sections are moved to an assembly station, where an assembler assembles the notched pieces and/or inserts keepers in the punched holes and assembles the muntins together.
A single blade or cutter is usually operated by an operator, who positions the muntin strips and presents them to the cutter. This operation is both slow and labor-intensive. It also does not assure consistent, high-quality parts. The second common technique, routing, leaves burrs that must be ground to secure a good fit. This, again, is time-consuming and labor-intensive. Because the many problem, including inconsistency, tend to result in insulated windows of questionable quality or longevity, an apparatus and method of producing consistent muntin sections and high-quality muntin assemblies in a shorter time period and at a reduced cost is highly desirable. It is to the solution of the above-mentioned problems to which the present invention pertains.